Unit 6b Absorption Diarrhea Cholera

Question 1

What is the primary driver of water absorption in the small intestine?
a) Active water pumps
b) Bile acid secretion
c) Passive chloride transport
d) Na+ absorption

Answer 1

d) Na+ absorption

Explanation: Sodium is absorbed through various transporters, and water follows osmotically through transcellular and paracellular routes.

Question 2

How are ions and water absorbed in the small and large intestine?
a) Water follows sugar absorption only
b) Active aquaporin-mediated water pumps
c) Through osmosis following ion gradients
d) Water is absorbed independently of solutes

Answer 2

c) Through osmosis following ion gradients

Explanation: Water absorption relies on osmotic gradients created by active transport of ions like Na+ and Cl−

Question 3

What transporter is involved in Na+ absorption in the gut?
a) CFTR
b) GLUT2
c) SGLT
d) Na+/K+-ATPase

Answer 3

d) Na+/K+-ATPase

Explanation: This pump on the basolateral membrane maintains the sodium gradient necessary for Na+ to enter from the apical side.

Question 4

What is the cholera toxins mechanism of action?
a) Activates CFTR causing massive Cl− and water secretion
b) Blocks sodium channels
c) Inhibits water absorption
d) Stimulates insulin release

Answer 4

a) Activates CFTR causing massive Cl− and water secretion

Explanation: Cholera toxin locks CFTR in the ‘on’ position, leading to excessive Cl− secretion and osmotic water loss, causing diarrhea.

Question 5

How does oral rehydration therapy (ORT) work for diarrhea?
a) Increases water diffusion across membranes
b) Uses glucose to enhance Na+ and water absorption
c) Stimulates mucus production
d) Blocks CFTR channels

Answer 5

b) Uses glucose to enhance Na+ and water absorption

Explanation: ORT takes advantage of the SGLT1 cotransporter that brings in Na+ and glucose together, pulling water with them.